A motor-vehicle door latch according to commonly owned U.S. Pat. No. 5,474,338 has a housing, a latching element movable in the housing between a latched position retaining a door bolt and an unlatched position releasing the door bolt, and a locking pawl engageable in the housing with the element and displaceable between a locked position retaining the latching element in the latched position and an unlocked position allowing the latching element to move into the unlatched position. Power actuation is effected by a planetary-gear drive in the housing centered on an axis and including a reversible electric motor, a sun gear rotatable by the motor about the axis, at least one planet gear meshing with the sun gear and orbitable about the axis, a planet carrier rotatable about the axis and carrying the planet gear, and a ring gear meshing with the planet gear and rotatable about the axis. A locking lever is displaceable in the housing by a locking element--a lock button or lock cylinder--and by the planet carrier between a locked position and an unlocked position and a coupling element is displaceable in the housing between a coupling position engaged between the locking pawl and locking lever for coupling the locking pawl and lever together for joint movement from the unlocked to the locked position and a uncoupling position permitting the locking lever to move between its position without moving the locking pawl. An antitheft element is displaceable in the housing by the sun gear between an antitheft-on position engageable with the coupling element and retaining same in the uncoupling position and an antitheft-off position permitting the coupling element to move between its positions. Structure in the housing coupled to the antitheft element arrests the planet carrier in the antitheft-on position of the antitheft element.
The problem with this system is that in the event of a power failure or some problem with the central-lock system, it is possible for the latch to be left in the antitheft-on position. In this case the latch is very difficult to open.